The present invention pertains to platens used in diverting conveyor systems and more particularly to an improved, longer lasting platen which securely transports a load and is wear resistant.
Diverting conveyors are well known in the art and are frequently used for the sorting or rejection of a series of articles that are being transported along a moving conveyor line. Diverting conveyors are also referred to as diverter tables or slat sorters. Typical diverting conveyors are described in U.S. Pat. No. 5,590,758 to Wilkins et al. and U.S. Pat. No. 3,986,596 to Hamilton. These generally utilize either push blocks or platens to carry articles along the conveyor. Platens utilized in such conveyors are slidably mounted to a series of moving tubes or rails extending between and carried by conveyor side-chains. The platens move with and selectively slide along the tubes in a direction transverse to the motion of the conveyor to define a path in a machine direction for a load thereon. In particular, the tubes are long enough to accommodate platens disposed in at least two paths as they move with the tubes. A follower pin located on the underside of the platen engages a cam, or guide track. A series of switches located at various points along the track are utilized to divert the pins and their associated platens and thus selectively direct successive platens and articles thereon laterally to one or more branches of the track as the platens move with the tubes in a machine direction. The flow of articles along various conveyor paths according to selected or detected parameters is thus provided.
Prior platens have been molded from a single type of plastic and have employed elongated non-skid elements, such as belts or tubes, pressed into grooves on a top surface of the platen for increased friction to better grip transported articles. Other prior platens have utilized a flat non-skid panel that is glued to an ultra-high molecular weight (UHMW) plastic platen body. A drawback of these prior platens is that the pressed belts or tubes tend to become unseated from the grooves and the panels tend to become unglued after a period of use. Such conditions allow articles to slide off the platens, creating the potential for jamming or binding which can damage both the article and the conveyor.
Accordingly, there is a need for a durable platen capable of providing extended service life and which has good wear-resistance and low frictional resistance for sliding on the conveyor tubes, yet also has a higher friction surface for gripping transported articles. Thus, it is an object of the invention to provide an improved diverting conveyor platen. It is another object of the invention to provide an improved diverting conveyor platen that has increased wear resistance, yet easily slides along the support tubes of a diverting conveyor. It is a further object of the invention to provide an improved diverting conveyor platen that does not come apart while in use.
The present invention provides an improved platen for use in diverting conveyor systems. The platen is formed from at least two different types of elastomeric material that are integrally co-molded, co-extruded, or otherwise processed together so as to provide a single unitary component which will not separate under operating conditions. The invention provides an advantage over prior platens in that the high friction support surface will not become unseated or unglued during service, thereby reducing the potential for damage and increasing the service life of the platen, while the body portion easily slides on supporting tubes and is resistant to wear.
The present invention contemplates an integral co-molded platen of two distinct materials. A main body portion is comprised of a relatively high durometer elastomeric material having good wear-resistance and a low friction coefficient for durability and ease of sliding on conveyor tubes. A preferred material is urethane with a hardness in the range of about 70 to 75 Shore-D durometer. A co-molded, integral support surface of the platen is integrally formed with the main body. The support surface is comprised of an elastomeric material which has a lower hardness than the main body and the support surface also has a higher friction coefficient for gripping transported articles. A preferred material is urethane with a hardness in the range of about 70 to 75 Shore-A durometer.
A platen diverting pin or cam follower is located on a bottom surface of the platen for engaging the guide track on a diverting conveyor. The pin can be molded into the body. In a preferred embodiment, however, an insert with a tapped hole is molded into the body and a threaded metallic pin is installed in the insert after the platen has been molded. In this way the pin may easily be replaced in the event that it becomes damaged or worn in service.
In another aspect of the invention, the platen body has beveled edges formed along the leading and trailing edges of the platen to reduce binding against a conveyed article, thereby reducing the potential for damage to the article or the conveyor.
In a further aspect of the invention, the surface of the body is contoured to positively engage the conveyor tubes.
In another aspect of the invention, the support surface includes contours that are formed into it to provide increased gripping of transported articles.
In yet another aspect of the invention, the main body is formed with an elastomeric filler that has lubricating qualities for providing increased slidability and wear-resistance as the surface of the body becomes abraded during use while sliding on the conveyor tubes. In a preferred embodiment, the filler consists of UHMW poly-beads in a matrix of urethane.
A preferred method for making an improved diverting conveyor platen in a mold includes the steps of: (a) positioning a tapped insert in a mold cavity; (b) filling the mold cavity with urethane in the range of 70-75 durometer, Shore D; (c) filling a second mold cavity with urethane in the range of 70-75 durometer, Shore A; (d) closing the mold; (e) applying heat and pressure, (f) opening the mold; and (g) removing the formed integral platen.
Accordingly, the invention provides a durable, integral platen which has a support surface made from a high friction material for gripping transported loads, and which has a main body made from a wear-resistant, low friction material for improved slidability on diverting conveyor tubes. The support surface and the main body are formed into a single, integral unit which will not separate under operating conditions. These and other aspects of the invention will be apparent from the following description, the claims, and the attached drawings.